Mia de los Reyes, PhD

I am an Assistant Professor of Astronomy at Amherst College. As an observational astronomer, I use low-mass galaxies in the nearby universe to answer the question: "Where did we come from?"

When I'm not doing research, I enjoy rock climbing, doing aerial silks, and eating baked goods.

Download my CV

I use multi-wavelength observations of nearby galaxies to understand how they form and evolve.
Below is a subset of my publication list. You can find a full list here:  ADS

First-author publications

• de los Reyes, M.A., Kirby, E.N., Zhuang, Z., Steidel, C.C., Chen, Y., Wheeler, C. (2023) Dwarfs In Void Environments (DIVE): The Stellar Kinematics of Void Dwarf Galaxies Using KCWI., ApJ, 951, 52, doi:10.3847/1538-4357/acd189
• de los Reyes, M.A., Kirby, E.N., Ji, A.P., Nuñez, E.H. (2021) Simultaneous Constraints on the Star Formation History and Nucleosynthesis of Sculptor dSph, ApJ, 925, 66, doi:10.3847/1538-4357/ac332b
• de los Reyes, M.A., Kirby, E.N., Seitenzahl, I.R., Shen, K.J. (2020) Manganese Indicates a Transition from Sub- to Near-Chandrasekhar Type Ia Supernovae in Dwarf Galaxies, ApJ, 891, 85, doi:10.3847/1538-4357/ab736f
• de los Reyes, M.A., Kennicutt, R.C. (2019) Revisiting the Integrated Star Formation Law. Paper I: Non-Starbursting Galaxies, ApJ, 872, 16, doi:10.3847/1538-4357/aafa82
• de los Reyes, M.A., Ly, C., Lee, J.C., et al. (2015) The Relationship Between Stellar Mass, Gas Metallicity, and Star Formation Rate for Hα-selected Galaxies at z ≈ 0.8 from the NewHα survey, AJ, 149, 79, doi:10.1088/0004-6256/149/2/79

Selected co-authored publications

• Zhuang, Z., Kirby, E.N., Leethochawalit, N., de los Reyes, M.A. (2021) NGC 147 Corroborates the Break in the Stellar Mass-Stellar Metallicity Relation for Galaxies, ApJ, 920, 63, doi:10.3847/1538-4357/ac1340
• Kennicutt, R.C., de los Reyes, M.A. (2021) Revisiting the Integrated Star Formation Law. Paper II: Starbursts and the Combined Global Schmidt Law, ApJ, 908, 61, doi:10.3847/1538-4357/abd3a2
• Shin, K., et al., including de los Reyes, M.A. (2021) Metal Abundances across Cosmic Time (MACT) Survey. III. The Relationship between Stellar Mass and Star Formation Rate in Extremely Low-Mass Galaxies, MNRAS, 502, doi:10.1093/mnras/staa3307
• Kirby, E.N., et al., including de los Reyes, M.A. (2019) Evidence for Sub-Chandrasekhar Type Ia Supernovae from Stellar Abundances in Dwarf Galaxies, ApJ, 881, 45, doi:10.3847/1538-4357/ab2c02

Current research

Galaxies in cosmic voids

I study low-mass galaxies located in the emptiest parts of the universe: cosmic voids.

Although most of the matter in the universe is located in long, thin structures called "cosmic filaments," some galaxies live in the vast, low-density voids between these filaments. My goal is to compare galaxies in voids and filaments to learn about how their environments have shaped their evolution.

To do this, I'm using the Keck Cosmic Web Imager to study the compositions and motions of stars and gas in several nearby galaxies.

Results are coming soon! In the meantime, if you want to know more about this project, check out this outreach talk I gave at Caltech.

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Galactic archaeology

I use the chemical abundances of stars in nearby galaxies to learn about the progenitors of Type Ia supernovae.

Type Ia supernovae (the explosions of white dwarf stars) are widely used as "standardizable candles" to measure astrophysical distances... but we don't fully understand the physics behind these explosions. One way to test models is to measure the heavy elements produced by these supernovae.

In particular, I care about manganese, which is primarily produced by more massive white dwarfs. By measuring manganese in stars in nearby dwarf galaxies, I can determine what kind of white dwarfs might be involved in Type Ia explosions.

The first result from this work is out here! You can also read my blog post on Evan Kirby's website. The next part of this work, which will measure the delay-time distribution of Type Ia supernovae, will be out soon!

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^{Image credit: NASA/ESA}

Star formation laws

I try to understand what factors drive star formation in nearby galaxies.

The formation of stars from cold gas is an important part of galaxy evolution, but we still don't fully understand how this works on a galaxy-wide scale. In 1998, Rob Kennicutt found that for spiral and starburst galaxies, there was a strong relationship between the star formation rate (how fast stars form) and gas surface density (how much gas is in the galaxy): the star formation law.

This law has since been widely used as an approximate "recipe" in cosmological simulations. But this recipe is now >20 years old! So I'm working with Rob to revisit his original 1998 analysis.

Paper I (on non-starbursting galaxies) is here, and Paper II (on starbursts) is here! Paper III (using dust surface density as a proxy for gas surface density) is on its way.

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Here are some of the outreach and professional service activities I've participated in. Check out my CV for a more extensive list!

Invited public talks and other appearances

• Caltech 3 Minute Thesis competition: 2021 First Prize winner and People's Choice Award winner
• AAS Journal Author Series
• Not My Thesis, Ep. 3: A Caltech Letters podcast
• A Galactic Archaeological Dig: California Academy of Sciences Virtual NightLife series
• The Loneliest Galaxies in the Universe: Caltech Astronomy Public Lecture Series
• Stars Go Boom! But Why?: Astronomy on Tap Los Angeles

^{Photo: Christopher Marcade}

Selected previous activities

Astrobites: For 5 years, I was actively involved in Astrobites, an international graduate student collaboration that publishes daily summaries of recent astro/physics papers. You can check out my posts here! As a member of the admin committee, I helped make steering decisions and developed the collaboration's Code of Conduct. I previously chaired the diversity, equity, and inclusion committee, where I spearheaded several diversity-related initiatives in Astrobites, including the #BlackinAstro and Indigenous Astronomy series.

Gender Minorities and Women in PMA: I was a member of the organizing committee of Caltech Gender Minorities and Women in Physics, Math, and Astronomy, a group that aims to support folks of marginalized genders in the Caltech PMA division. I help plan and run regular events: social events, workshops, and journal clubs.

Here are some resources I've put together for people applying to grad school or people interested in improving department climate/admissions policies.

Grad app timeline

List of active faculty

NSF GRFP

Removing the PGRE

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I've made a timeline for applying to astro PhD programs (specifically at Caltech, but it should also be relevant for other grad programs), with tips about each part of the application. Parts of this guide are adapted from a presentation by Ivanna Escala, as well as this excellent Astrobite.

Download online version Download printable version

I worked with fellow grad students to start a list of astronomy and planetary sciences faculty in the US who are actively taking students. The list includes searchable keywords describing faculty members' research interests, as well as contact information for some of their past/current students. If you're applying to grad school, you can use this when deciding where to apply, when writing your personal statements, or when contacting faculty/students.

View list

Below are my essays for the NSF Graduate Research Fellowship Program. If you're applying for this fellowship, please feel free to contact me; I'm happy to send you my reviewer comments and answer any questions you might have. Also check out other essays on this website by Alex Lang!

My personal statement My research proposal

I helped push to get rid of the Physics GRE (PGRE) as a requirement for our graduate admissions process. With the help of some fellow grad students, I wrote up a document with reasons why Caltech Astro should remove the PGRE requirement, which was circulated among students and faculty.

Download PGRE FAQ

Some other things I've written

• Where do we go from here?: An essay about the proposed Thirty-Meter Telescope on the sacred peak of Maunakea
• A guide to applying to astro postdocs: A two-part series (Part 1, Part 2) on applying for postdocs in astro/physics, co-authored with Dr. Luna Zagorac

Want me to give a talk or participate in a science outreach event? Have questions about the resources I've posted here? Please feel free to contact me at: mdelosreyes at amherst.edu